The present invention relates to therapeutic compositions and methods for the treatment or diagnosis of diseases or conditions related to NF-xcexaB levels, such as restenosis, rheumatoid arthritis, asthma, inflammatory or autoimmune disorders and transplant rejection.
The following is a brief description of the physiological role of NF-xcexaB. The discussion is not meant to be complete and is provided only for understanding of the invention that follows. This summary is not an admission that any of the work described below is prior art to the claimed invention.
The nuclear DNA-binding activity, NF-xcexaB, was first identified as a factor that binds and activates the immunoglobulin xcexa light chain enhancer in B cells. NF-xcexaB now is known to activate transcription of a variety of other cellular genes (e.g., cytokines, adhesion proteins, oncogenes and viral proteins) in response to a variety of stimuli (e.g., phorbol esters, mitogens, cytokines and oxidative stress). In addition, molecular and biochemical characterization of NF-xcexaB has shown that the activity is due to a homodimer or heterodimer of a family of DNA binding subunits. Each subunit bears a stretch of 300 amino acids that is homologous to the oncogene, v-rel. The activity first described as NF-xcexaB is a heterodimer of p49 or p50 with p65. The p49 and p50 subunits of NF-xcexaB (encoded by the nf-xcexaB2 or nf-xcexaB1 genes, respectively) are generated from the precursors NF-xcexaB1 (p105) or NF-xcexaB2 (p100). The p65 subunit of NF-xcexaB (now termed Rel A ) is encoded by the rel A locus.
The roles of each specific transcription-activating complex now are being elucidated in cells (N. D. Perkins, et al., 1992 Proc. Natl Acad. Sci USA 89, 1529-1533). For instance, the heterodimer of NF-xcexaB1 and Rel A (p50/p65) activates transcription of the promoter for the adhesion molecule, VCAM-1, while NF-xcexaB2/RelA heterodimers (p49/p65) actually inhibit transcription (H. B. Shu, et al., Mol. Cell. Biol. 13, 6283-6289 (1993)). Conversely, heterodimers of NF-xcexaB2/RelA (p49/p65) act with Tat-I to activate transcription of the HIV genome, while NF-xcexaB1/RelA (p50/p65) heterodimers have little effect (J. Liu, N. D. Perkins, R. M. Schmid, G. J. Nabel, J. Virol. 1992 66, 3883-3887). Similarly, blocking rel A gene expression with antisense oligonucleotides specifically blocks embryonic stem cell adhesion; blocking NF-xcexaB1 gene expression with antisense oligonucleotides had no effect on cellular adhesion (Narayanan et al., 1993 Mol. Cell. Biol. 13, 3802-3810). Thus, the promiscuous role initially assigned to NF-xcexaB in transcriptional activation (M. J. Lenardo, D. Baltimore, 1989 Cell 58, 227-229) represents the sum of the activities of the rel family of DNA-binding proteins. This conclusion is supported by recent transgenic xe2x80x9cknock-outxe2x80x9d mice of individual members of the rel family. Such xe2x80x9cknock-outsxe2x80x9d show few developmental defects, suggesting that essential transcriptional activation functions can be performed by more than one member of the rel family.
A number of specific inhibitors of NF-xcexaB function in cells exist, including treatment with phosphorothioate antisense oliogonucleotide, treatment with double-stranded NF-xcexaB binding sites, and over expression of the natural inhibitor MAD-3 (an IxcexaB family member). These agents have been used to show that NF-xcexaB is required for induction of a number of molecules involved in inflammation, as described below.
NF-xcexaB is required for phorbol ester-mediated induction of IL-6 (I. Kitajima, et al., Science 258, 1792-5 (1992)) and IL-8 (Kunsch and Rosen, 1993 Mol. Cell. Biol. 13, 6137-46).
NF-xcexaB is required for induction of the adhesion molecules ICAM-1 (Eck, et al., 1993 Mol. Cell. Biol. 13, 6530-6536), VCAM-1 (Shu et al., supra), and E-selectin (Read, et al., 1994 J. Exp. Med. 179, 503-512) on endothelial cells.
NF-xcexaB is involved in the induction of the integrin subunit, CD18, and other adhesive properties of leukocytes (Eck et al., 1993 supra).
The above studies suggest that NF-xcexaB is integrally involved in the induction of cytokines and adhesion molecules by inflammatory mediators. Two recent papers point to another connection between NF-xcexaB and inflammation: glucocorticoids may exert their anti-inflammatory effects by inhibiting NF-xcexaB. The glucocorticoid receptor and p65 both act at NF-xcexaB binding sites in the ICAM-1 promoter (van de Stolpe, et al., 1994 J. Biol. Chem. 269, 6185-6192). Glucocorticoid receptor inhibits NF-xcexaB-mediated induction of IL-6 (Ray and Prefontaine, 1994 Proc. Natl Acad. Sci USA 91, 752-756). Conversely, overexpression of p65 inhibits glucocorticoid induction of the mouse mammary tumor virus promoter. Finally, protein cross-linking and co-immunoprecipitation experiments demonstrated direct physical interaction between p65 and the glucocorticoid receptor (Id.).
This invention relates to ribozymes, or enzymatic RNA molecules, directed to cleave mRNA species encoding Rel A protein (p65). In particular, applicant describes the selection and function of ribozymes capable of cleaving this RNA and their use to reduce activity of NF-xcexaB in various tissues to treat the diseases discussed herein. Such ribozymes are also useful for diagnostic applications.
Ribozymes that cleave rel A mRNA represent a novel therapeutic approach to inflammatory or autoimmune disorders. Antisense DNA molecules have been described that block NF-xcexaB activity. See Narayanan et al., supra. However, ribozymes may show greater perdurance or lower effective doses than antisense molecules due to their catalytic properties and their inherent secondary and tertiary structures. Such ribozymes, with their catalytic activity and increased site specificity (as described below), represent more potent and safe, therapeutic molecules than antisense oligonucleotides.
Applicant indicates that these ribozymes are able to inhibit the activity of NF-xcexaB and that the catalytic activity of the ribozymes is required for their inhibitory effect. Those of ordinary skill in the art, will find that it is clear from the examples described that other ribozymes that cleave rel A encoding mRNAs may be readily designed and are within the invention.
Six basic varieties of naturally-occurring enzymatic RNAs are known presently. Each can catalyze the hydrolysis of RNA phosphodiester bonds in trans (and thus can cleave other RNA molecules) under physiological conditions. Table I summarizes some of the characteristics of these ribozymes. In general, enzymatic nucleic acids act by first binding to a target RNA. Such binding occurs through the target binding portion of a enzymatic nucleic acid which is held in close proximity to an enzymatic portion of the molecule that acts to cleave the target RNA. Thus, the enzymatic nucleic acid first recognizes and then binds a target RNA through complementary base-pairing, and once bound to the correct site, acts enzymatically to cut the target RNA. Strategic cleavage of such a target RNA will destroy its ability to direct synthesis of an encoded protein. After an enzymatic nucleic acid has bound and cleaved its RNA target, it is released from that RNA to search for another target and can repeatedly bind and cleave new targets.
The enzymatic nature of a ribozyme is advantageous over other technologies, such as antisense technology (where a nucleic acid molecule simply binds to a nucleic acid target to block its translation) since the concentration of ribozyme necessary to affect a therapeutic treatment is lower than that of an antisense oligonucleotide. This advantage reflects the ability of the ribozyme to act enzymatically. Thus, a single ribozyme molecule is able to cleave many molecules of target RNA. In addition, the ribozyme is a highly specific inhibitor, with the specificity of inhibition depending not only on the base pairing mechanism of binding to the target RNA, but also on the mechanism of target RNA cleavage. Single mismatches, or base-substitutions, near the site of cleavage can completely eliminate catalytic activity of a ribozyme. Similar mismatches in antisense molecules do not prevent their action (Woolf, T. M., et al., 1992, Proc. Natl. Acad. Sci. USA, 89, 7305-7309). Thus, the specificity of action of a ribozyme is greater than that of an antisense oligonucleotide binding the same RNA site.
In preferred embodiments of this invention, the enzymatic nucleic acid molecule is formed in a hammerhead or hairpin motif, but may also be formed in the motif of a hepatitis delta virus, group I intron or RNaseP RNA (in association with an RNA guide sequence) or Neurospora VS RNA. Examples of such hammerhead motifs are described by Rossi et al., 1992, Aids Research and Human Retroviruses, 8, 183, of hairpin motifs by Hampel et al., xe2x80x9cRNA Catalyst for Cleaving Specific RNA Sequences,xe2x80x9d filed Sep. 20, 1989, which is a continuation-in-part of U.S. Ser. No. 07/247,100 filed Sep. 20, 1988, Hampel and Tritz, 1989, Biochemistry, 28, 4929, and Hampel et al., 1990, Nucleic Acids Res.earch, 18,299, and an example of the hepatitis delta virus motif is described by Perrotta and Been, 1992, Biochemistry, 31, 16, of the RNaseP motif by Guerrier-Takada et al., 1983,Cell, 35, 849, Neurospora VS RNA ribozyme motif is described by Collins (Saville and Collins, 1990 Cell 61, 685-696; Saville and Collins, 1991 Proc. Natl. Acad. Sci. USA 88, 8826-8830; Collins and Olive, 1993 Biochemistry 32, 2795-2799) and of the Group I intron by Cech et al., U.S. Pat. No. 4,987,071. These specific motifs are not limiting in the invention and those skilled in the art will recognize that all that is important in an enzymatic nucleic acid molecule of this invention is that it has a specific substrate binding site which is complementary to one or more of the target gene RNA regions, and that it have nucleotide sequences within or surrounding that substrate binding site which impart an RNA cleaving activity to the molecule.
The invention provides a method for producing a class of enzymatic cleaving agents which exhibit a high degree of specificity for the RNA of a desired target. The enzymatic nucleic acid molecule is preferably targeted to a highly conserved sequence region of a target Rel A encoding mRNA such that specific treatment of a disease or condition can be provided with either one or several enzymatic nucleic acids. Such enzymatic nucleic acid molecules can be delivered exogenously to specific cells as required. Alternatively, the ribozymes can be expressed from DNA vectors that are delivered to specific cells.
Synthesis of nucleic acids greater than 100 nucleotides in length is difficult using automated methods, and the therapeutic cost of such molecules is prohibitive. In this invention, small enzymatic nucleic acid motifs (e.g., of the hammerhead or the hairpin structure) are used for exogenous delivery. The simple structure of these molecules increases the ability of the enzymatic nucleic acid to invade targeted regions of the mRNA structure. However, these catalytic RNA molecules can also be expressed within cells from eukaryotic promoters (e.g., Scanlon, K. J., et al., 1991, Proc. Natl. Acad. Sci. USA, 88, 10591-5; Kashani-Sabet, M., et al., 1992, Antisense Res. Dev., 2, 3-15; Dropulic, B., et al., 1992, J Virol, 66, 1432-41; Weerasinghe, M., et al., 1991, J Virol, 65, 5531-4; Ojwang, J. O., et al., 1992, Proc. Natl. Acad. Sci. USA, 89, 10802-6; Chen, C. J., et al., 1992, Nucleic Acids Res., 20, 4581-9; Sarver, H., et al., 1990, Science, 247, 1222-1225)). Those skilled in the art realize that any ribozyme can be expressed in eukaryotic cells from the appropriate DNA vector. The activity of such ribozymes can be augmented by their release from the primary transcript by a second ribozyme (Draper et al., PCT WO93/23569, and Sullivan et al., PCT WO94/02595, both hereby incorporated in their totality by reference herein; Ohkawa, J., et al., 1992, Nucleic Acids Symp. Ser., 27, 15-6; Taira, K., et al., 1991, Nucleic Acids Res., 19, 5125-30; Ventura, M., et al., 1993, Nucleic Acids Res., 21, 3249-55) .
Inflammatory mediators such as lipopolysaccharide (LPS), interleukin-1 (IL-1) or tumor necrosis factor-a (TNF-xcex1) act on cells by inducing transcription of a number of secondary mediators, including other cytokines and adhesion molecules. In many cases, this gene activation is known to be mediated by the transcriptional regulator, NF-xcexaB. One subunit of NF-xcexaB, the relA gene product (termed RelA or p65) is implicated specifically in the induction of inflammatory responses. Ribozyme therapy, due to its exquisite specificity, is particularly well-suited to target intracellular factors that contribute to disease pathology. Thus, ribozymes that cleave mRNA encoded by rel A may represent novel therapeutics for the treatment of inflammatory and autoimmune disorders.
Thus, in a first aspect, the invention features ribozymes that inhibit RelA production. These chemically or enzymatically synthesized RNA molecules contain substrate binding domains that bind to accessible regions of their target mRNAs. The RNA molecules also contain domains that catalyze the cleavage of RNA. The RNA molecules are preferably ribozymes of the hammerhead or hairpin motif. Upon binding, the ribozymes cleave the target RelA encoding mRNAs, preventing translation and p65 protein accumulation. In the absence of the expression of the target gene, a therapeutic effect may be observed.
By xe2x80x9cinhibitxe2x80x9d is meant that the activity or level of RelA encoding mRNA is reduced below that observed in the absense of the ribozyme, and preferably is below that level observed in the presence of an inactive RNA molecule able to bind to the same site on the mRNA, but unable to cleave that RNA.
Such ribozymes are useful for the prevention of the diseases and conditions discussed above, and any other diseases or conditions that are related to the level of NF-xcexaB activity in a cell or tissue. By xe2x80x9crelatedxe2x80x9d is meant that the inhibition of relA mRNA and thus reduction in the level of NF-xcexaB activity will relieve to some extent the symptoms of the disease or condition.
Ribozymes are added directly, or can be complexed with cationic lipids, packaged within liposomes, or otherwise delivered to target cells. The RNA or RNA complexes can be locally administered to relevant tissues ex vivo, or in vivo through injection or the use of a catheter, infusion pump or stent, with or without their incorporation in biopolymers. In preferred embodiments, the ribozymes have binding arms which are complementary to the sequences in Tables II, III, VI-VII. Examples of such ribozymes are shown in Tables IV-VII. Examples of such ribozymes consist essentially of sequences defined in these Tables. By xe2x80x9cconsists essentially ofxe2x80x9d is meant that the active ribozyme contains an enzymatic center equivalent to those in the examples, and binding arms able to bind mRNA such that cleavage at the target site occurs. Other sequences may be present which do not interfere with such cleavage.
In another aspect of the invention, ribozymes that cleave target molecules and inhibit NF-xcexaB activity are expressed from transcription units inserted into DNA, RNA, or viral vectors. Preferably, the recombinant vectors capable of expressing the ribozymes are locally delivered as described above, and transiently persist in target cells. Once expressed, the ribozymes cleave the target mRNA. The recombinant vectors are preferably DNA plasmids or adenovirus vectors. However, other mammalian cell vectors that direct the expression of RNA may be used for this purpose.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.